A series of biophysical studies on the visual pigment rhodopsin are proposed. The ultimate goal of these studies is to gain a more detailed understanding of the structure of rhodopsin and how this relates to its function and interactions with other components of the rod outer segments. A variety of chemical, physical, spectroscopic and microscopic techniques will be used in these studies. 1) Two-dimensional crystals of bovine rhodopsin will be formed and characterized. Optial diffraction and reconstruction techniques will be used to obtain a spatially filtered two-dimensional projection map of negatively stained crystalline sheets. Eventually the three-dimensional structure will be determined using low dose electron microscopy, surface shadowing, and correlated X-ray diffraction techniques. Using chemical and macromolecular labels specific functional important regions of the molecule will be mapped onto the structure. 2) Hydrodynamic methods will be used to determine the association state of rhodopsin in detergent solutions to ascertain the role of protein-protein association in stabilizing the protein. 3) These methods will also be used to explore potential direct interactions between rhodopsin and other proteins of the rod outer segment whose activities are modulated by light. 4) Kinectic and thermodynamic analyses will be lused to evaluate the effect of the partitioning of retinal into detergents and phospholipid bilayers on the protein's ability to recombine with 11-cis retinal after being bleached. 5) Rhodopsin in various detergent solutions will be characterized by its absorption and ciruclar dichroic (both UV and visible) spectra, thermal stability and kinetic properties. 6) The intact bovine retina will be studied by electron microscopy (thin section) to round out the data on the source of terinal material used most often in biochemical studies. These studies will, hopefully, further our knowledge on the processes involved in vision.